A modified phase‐based constitutive model for shape memory polymers

Abstract

Constitutive models used for predicting the thermomechanical behavior of shape memory polymers (SMPs) are critical for the development of SMP applications. Among the existing models, the phase transition concept attracts wide attention due to its good predictive capacity and great convenience. However, most of the present phase transition models for SMPs have limitations or deficiencies in considering the effect of temperature change rate on the thermomechanical behavior of SMPs. In this paper, based on the kinetics of phase transitions, we propose a constitutive model in which the temperature change rate is incorporated into the phase evolution function to consider the effect of the temperature change rate on the thermomechanical properties of SMPs. Then experimental data under different recovery conditions for two different types of SMP materials are used to validate the predictive capacity and versatility of the present model. The predicted results agree quite well with the experimental observations, which demonstrates that the present model is robust enough to predict the complex thermomechanical behavior for different SMPs. In addition, through experiments and model predictions, we find that the shape free recovery curves at different heating rates can be easily predicted by just moving a reference recovery curve along the horizontal direction by a distance whose value is calculated through the proposed equation. © 2018 Society of Chemical Industry

A comprehensive review on thermomechanical constitutive models for shape memory polymers

“…Pan et al (2018) based on the model provided by Liu et al (2006), and considering a rate-dependent T trans , developed a new constitutive model and calibrated the model for the polystyrene and an acrylate-based SMP (tBA/PEGDMA), for test results of Arrieta et al (2014b). In line with work of Wang et al (2009), Guo et al (2017) introduced another function for the frozen phase volume fraction.…”

Mechanical Models, Structures, and Applications of Shape-Memory Polymers and Their Composites

“…In addition, considering the large difference of Young's modulus between the frozen and active states, the mixing law cannot accurately predict the equivalent modulus of SMPs. Wang Considering the influence of heating/cooling rate, a new constitutive model for predicting the mechanical response of different SMPs at different recovery conditions (free recovery, fixed-stress recovery, and different heating rates) was proposed by Liu [57]. Lu et al proposed a physically significant phenomenological model of "frozen volume" caused by internal stress and dominated by the two-site model theory.…”

Cooperative principle in multiple glass transitions and strain relaxations of thermochemically responsive shape memory polymer

“…Among all different types of SMPs, thermally activated amorphous SMPs are the most investigated ones because of their wide variety, simplicity in synthesis, widely available characterization methods and constitutive models [6][7][8]. Taking for example, Liu et.al proposed a useful viscoelastic model for SMP according to the phase transition, and it well predicted the thermomechanical and time-dependent shape recovery behaviors [9][10][11].…”